Monitoring the Chilean Subduction zone

ZIP Consolidator (WP4.3): Onland continuous monitoring of the Chilean subduction interface / 2 weeks, M-25 — Coordination: O. Oncken (GFZ) + UCN. Contributors: M. Moreno (GFZ), C. Vigny (CNRS), C. Ranero (CSIC).
This training has taken place together with the second annual workshop in Antofagasta (M-25) and will focus on instrumental training onland in the northern Chile seismic gap, which is an area of high seismic hazard. Through a 10 day course comprising field work and observatory visit, all network members got the unique practical opportunity to access continuous monitoring of the subduction interface and exchange on the results already obtained on the active (Mediterranean and Chilean) and fossil (Alpine, Chinese) subduction zones.
The training event consisted of an introductory course to the principles and applications of geodetic and geophysical data to monitoring an active subduction zone. This was followed up by a field excursion along exceptional geological environments of the Northern Chile forearc and western Andes aimed at visiting the tectonics, structure and geological history of a major tectonic segment boundary.
The course provided fundamental concepts of modern monitoring techniques at active subduction zones, and most specifically on the interdisciplinary strategies of the IPOC observatory. All theoretical material taught in the course was supported by exercises and simulations, which provided to the participants a direct practical experience that incorporates hands-on learning realistic data simulations.

Workshop detailsDate: 5-9/10/2015. Location: Antofagasta, Chile. Organisers: GFZ-Potsdam team
5 days of indoor lectures by ZIP supervisors and external scientists (see appended list) focused on the use of GPS observations and kinematic modeling, and how they are applied to the study of earthquake related deformation. Participants gained a comprehensive understanding of all components of using geodetic data in the study of earthquakes, including data collection, processing, accuracy, and numerical simulation of observed deformation. In addition, it was presented an introduction to fundamental seismic principles applied to the study of the subduction interface and a short course of the basic concepts of deformation and fluid-rock interaction in ancient subduction interfaces. Several presentations examined some aspects of the paradox between short- and long term deformations, crustal fault activity, tectonics control on the Andean Orogen, active seismicity in the Chilean subduction zone, and real time monitoring of earthquake deformation.Agenda & Speakers:Day 1
Fundamental concepts of the subduction zone earthquake cycle (Marcos Moreno)
Practical training: 2D Meshing (Paraskevi Io Ioannidi)
Practical training: Modeling an elastic seismic cycle with Pylith (Marcos Moreno)
Practical training session on using GPS receivers (Mahesh Shrivastava & Marcos Moreno)Day 2
Fieldwork: Visiting a continuous GPS station.
Introduction to GPS processing (Mahesh Shrivastava)
Practical training: Modeling a visco-elastic seismic cycle with Pylith (Marcos Moreno)Day 3
Fundamentals of Geodesy (Chris Vigny)
Basics of GPS measurements: uncertainties/precision/errors (Chris Vigny)
Exercise: Computing Strain and Rotation rates in a GPS network (Chris Vigny)
Exercise: Finding and applying a rigid rotation pole to a velocity field (Chris Vigny)
Exercise: Dynamic model of rupture propagation in Pylith (Gianina Meneses)
Practical training: Example of 3D modeling of Chilean subduction zone (Marcos Moreno)Day 4
Inverting a velocity field around a faults (Chris Vigny)
Example of FE-model derived Green Functions for slip inversion (Marcos Moreno)
Introduction to global and local seismic networks and instrumentation
The Integrated Plate boundary Observatory Chile (IPOC) (Bernd Schurr)
The seismic architecture of subduction zones with a focus on northern Chile (Bernd Schurr)Day 5
Subduction along Chile and orogeny – from earthquakes to mountains (Onno Oncken)
Chilean Subduction earthquakes (Sergio Ruiz)
Active Faults in northern Chile – observations from 106 y to seconds (Pia Victor)
25 years of GPS in Chile: what did we learn? (Chris Vigny)
GNSS in the Centro Sismológico Nacional (Juan Carlos Baez)
Inversion of static displacements due to large interplate earthquakes: towards real-time monitoring (Francisco del Campo)
Course: Deformation and fluid-rock interaction in ancient subduction interfaces (Samuel Angiboust)

Excursion Days 6- 11
The megathrust plate boundary between the continental South American and the oceanic Nazca plates routinely generates megathrust earthquakes (Mw > 8.5) and drives the spectacular Andean orogen. The field trip took advantage of exceptional geological environments and awe inspiring landscapes in the area of the Northern Chile forearc and Andes west flank to further the knowledge of active margin processes. The fieldwork covered core topics including active tectonics, structur and geological history of the region, and volcanology. We studied various locations to observe how landforms can be created and modified by tectonic processes and how geomorphology can be used to interpret the nature of tectonic activity and processes at the underlying subduction zone. To understand the relation between the tectonic evolution of the Andes and the geo-resources we also visited the Chuquicamata mine, which is the biggest open pitcoppermine in the world.

The north of Chile is one of the most carefully monitored plate boundary systems in the world. Here, The International Plate boundary Observatory Chile (IPOC) uses a wide range of geophysical and geodetic instruments to improve our understanding of both the physical mechanisms underlying the earthquake processes and the natural hazards induced by them. In contrast to conventional observatories that monitor an individual signal only, IPOC is designed to capture a large range of different, possibly associated deformation processes by using different geophysical and geological observation methods (seismographs, strong-motion seismographs, GPS, magnetotelluric sensors, creepmeter, accelerometer, InSAR, etc.). During the fieldtrip we also visited a multi-parameter IPOC station.

Day 6 – Thursday 15th of October
Visit to IPOC station PB06.
Fault rupture at the Salar del Carmen segment of the Atacama Fault System and + creepmeter observations (Pia Victor).
Overnight stay: Antofagasta.